Update: Is a belated 'super' El Niño in the works for 2015?
Friday, May 15, 2015, 4:33 PM - What's going on in the central Pacific Ocean? After teasing NOAA forecasters throughout 2014, and getting an unusually early start this year, it's looking more and more like El Niño 2015 will persist throughout the year, and possibly even grow stronger.
Earlier this week, the Australian Bureau of Meteorology released a statement, saying that conditions in the equatorial Pacific Ocean had developed enough for their forecasters to confirm an El Niño for 2015. As of today, Thursday, May 14, NOAA - the US National Oceanic and Atmospheric Administration - issued their own updated forecast, stating that the weak central Pacific El Niño that had been called back in March had strengthened and spread towards the east, developing into a more "classic" El Niño scenario.
As it stands now, NOAA forecasters give a 90 per cent probability that El Niño will persist at least through the summer months of 2015, and an 80 per cent chance that it will still be around by the end of the year.
What will this mean for 2015?
While confidence levels in how long this El Niño will last are quite high, confidence in exactly how strong it will become are somewhat lower.
Model forecasts of central Pacific sea surface temperature anomalies (shown below in degrees Celsius) definitely favour strengthening El Niño conditions. Anything above 2oC on the graph is considered to be a "super" El Niño.
Model predictions for sea surface temperature anomaly (oC) for the central Pacific. Credit: NOAA
Forecasts from the Australian Bureau of Meteorology and the Japan Meteorological Agency also favour a stronger El Niño. However these forecasts level it off as a "significant" event - strong, but not like it was in 1997/98 (which topped out at a sea surface temperature anomaly of +2.4oC).
Given that the NOAA and NASA models were also calling for a "super" El Nino in 2014, there's a reluctance to assign too much weight to their results this year. The JMA model, by contrast, performed so much better with the strangeness of last year. So, while El Niño will almost certainly strengthen into summer, a moderate result - between 1.5-2.0oC - is more likely than a super El Niño.
That said, if the pattern does persists into autumn and winter, there's a chance it may strengthen even more. If some of the more aggressive forecasts pan out, it's even possible that it could become the strongest El Niño on record.
What will this do for Canada's weather? Will we see a mild winter?
As for what kind of effects we could see on the weather this year:
For tropical cyclones, the development of an El Niño typically impacts the formation of Atlantic hurricanes, reducing the number that spin up during the season. An early look at the Atlantic hurricane forecast is already seeing a quiet season this year, and this may result in even lower numbers when the official forecast comes out later this month.
For other weather patterns, an El Niño that peaks in late fall/early winter usually brings warmer, drier weather to the western half of Canada, and cooler weather to the north. If this year's pattern peaks in summer or fall instead, the warmer, drier weather may result in a hotter, drier summer and fall for much of Canada, but it could bring some relief to the warmer Arctic, and slow the rate of sea ice melt.
As for whether or not we can look forward to a mild winter in 2015/2016 depends on how strong this El Niño gets and how long it persists. If it peaks in summer and tapers off, we may end up with a winter very much like what we just went through in 2014/15 (and possibly worse if there's more rainfall and moisture in California to fuel Colorado Lows). If the pattern persists and peaks in winter, we may actually get the more mild winter everyone hopes for from an El Niño.
Beyond that, there's simply not enough examples of this kind of early/persistent El Niño to form a trend, plus it's still too early in the year, and there are too many uncertainties, to say what will happen for sure.
What's going on?
The situation in the equatorial Pacific Ocean has been a bit of a head-scratcher over the past year.
Last May, word spread through some media channels of a coming "super" El Niño, the likes of which haven't been seen since 1997/98. These predictions failed to pan out, though. Sea surface temperatures in the Pacific were certainly above normal, but the atmosphere just didn't seem to want to "get with the program."
While conditions didn't back off completely, as they have done in the past, they teased forecasters with a slow, delayed response. Finally, in early March, we ended up with a weak El Niño Modoki, where warmer sea surface temperatures are concentrated around the middle of the ocean, rather than in the region that typically sees the warmest ocean waters - off the coastlines of Peru and Ecuador.
In a typical El Niño scenario, ocean temperatures warm up off the coastlines of Ecuador and Peru throughout the spring, summer and fall, and the strong easterly winds that blow across from South America to Australia break down into several smaller atmospheric cells. This results in a full-developed situation where ocean temperatures peak going into winter, then cool off through the season and return to 'normal' by late spring.
Sea surface temperatures above/below normal across the Pacific. Credit: NOAA Climate Prediction Center
As of the latest looks at the developing conditions, and the latest computer model runs, it seems that everything is lining up to result in a more "classic" El Niño. However, it's anything but typical.
Rather than emulating 1997/98, as it seemed was happening a year ago, El Niño 2015 has apparently chosen a path of development few other El Niños have followed in the past, at least in the 60 years that we've been monitoring it.
According to NOAA researcher and ENSO blogger Emily Becker, the development of this year's "special snowflake" is following a course similar to the 1986-1987 El Niño, and it's only the second time we've seen this in the record books.
Credit: Climate.gov from CPC data
In this scenario, a slow buildup over the course of one year leads to El Niño conditions that persist straight through the following year.
In the '80s, this resulted in an unusual "double-peak" El Niño that ramped up in late '86, peaked twice in '87 (first in Jan-Feb-Mar and then a stronger second peak by Jul-Aug-Sep), and then finally abated in early 1988. According to NOAA's records, this was also the longest uninterrupted period of El Niño conditions on record.
Even though this year seems to be developing along the same lines as conditions in 1987, looking back to that year really doesn't help. The world is simply a different place than it was 28 years ago.
The North Pacific is far warmer now than it was in 1987, due to The Blob. The world is also an overall warmer place. On the list of warmest years on record, 1987 currently ranks somewhere in the 20s, whereas 2014 is now the warmest year on record. Additionally, the last 12 months rank as the hottest 12-month period on record, and 2015 is setting records on its own as well.
Coupled with what's going on in the Arctic - where temperatures are significantly warmer and there's more than a million square kilometres more open water now compared to 1987 - it's difficult to make comparisons.
(Hat-tip to Dr. Doug Gillham for his invaluable input.)